Field of the Invention
The present invention relates to a die cushion device and a method of controlling the die cushion device, and more particularly to a technique of improving responsivity of action of cushion force.
Description of the Related Art
In a press machine including a die cushion device, there has been known a die cushion device that controls hydraulic pressure (die cushion force) in a cap side hydraulic chamber of a hydraulic cylinder supporting a cushion pad by using a servo motor for driving a hydraulic pump connected to cap side hydraulic chamber, or a servo valve (refer to Japanese Patent Application Laid-Open No. 2006-315074 (Patent Literature 1) and Japanese Patent Application Laid-Open No. 2006-142312 (Patent Literature 2)).
Japanese Patent Application Laid-Open No. 2006-130524 (Patent Literature 3) describes a die cushion mechanism provided with a control device that causes required die cushion force to be properly generated with high responsivity by using slide speed when controlling force of a servo motor for driving the die cushion mechanism.
Japanese Patent Application Laid-Open No. 2006-130533 (Patent Literature 4) describes a control device of a servo motor, the control device achieving high responsivity in terms of control by using command correction means for controlling pressure when force is applied to a driven body to be driven by the servo motor.
Japanese Patent Application Laid-Open No. 2006-255743 (Patent Literature 5) describes a die cushion control device that achieves high responsivity in terms of control by controlling a command to increase pressure, thereby allowing high cushion pressure, required to hold a work, to be promptly generated, and that reduces fluctuations in cushion pressure to enable a product to be favorably formed.
Japanese Patent Application Laid-Open No. 10-192997 (Patent Literature 6) describes a method of controlling die cushion, the method achieving high responsivity in terms of control by switching between position control and pressure control by position detection of a cushion cylinder, and by the pressure control by a proportion (P)/integration (I) control command and a bias signal.
Meanwhile, there is typically conceived a method of controlling die cushion force in which a cushion pad is put on standby at a position above a die cushion standby position by a predetermined amount, and die cushion force is increased to a setting value in a period where the cushion pad descends to the die cushion standby after a slide collides with the cushion pad (or within response delay time of the die cushion force).